Frozen Condensate Pipe

What is a condensate pipe?

A condensate pipe carries condensation from your boiler to your outside drain. It’s usually a white or grey plastic pipe that travels from your boiler through the wall directly outside where your boiler is located. During cold weather, the condensation in this pipe may freeze and cause a blockage causing the condensation to back up into the boiler and cause it to shut down

Step-by-step guide

If you suspect that your boiler condensate pipe has frozen, the following steps should help you get things back to normal quickly.
Remember, if you don’t feel confident when following this guide then you should contact an expert boiler engineer for help.

Confirm the condensate pipe is frozen

Depending on the make and model of your boiler, a frozen condensate pipe may be indicated by a ‘fault code’ or warning light on the boiler’s display. Gurgling or bubbling sounds coming from the boiler or the condensate pipe are another sign that the condensate pipe has frozen.

Locate the blockage

The pipe is probably frozen at its most exposed point. This may be the open end of the pipe, or at a bend or elbow. Running your hands over the pipe until you find a section that feels colder than the rest should help you identify the blockage quickly.

Use hot water to thaw the pipe

Using a jug or watering can, pour hot water along the length of the pipe, repeating the process until the pipe has thawed (do not use boiling water as this can crack or damage the pipe). If you’re using a kettle, make sure to cool the kettle for at least 15 minutes once it’s boiled. 

Restart your boiler

Once the frozen section has been melted and cleared, check your boiler manual for instructions on how to reset the boiler correctly. Your boiler should now restart.

Not fixed? Keep trying

It may take several attempts before your boiler restarts, but if it doesn’t, you may need to call out a qualified boiler engineer.

Be careful where you pour the water too – it may freeze and become a slip-hazard

How to stop your condensate pipe from freezing

If your condensate pipe isn’t already insulated, wrap it in some old towels immediately to prevent it freezing again. As soon as you can, get down to your local DIY store and buy some foam pipe insulation to wrap the condensate pipe in (just make sure to check it’s for external use). This insulation comes in a variety of sizes, so measure the pipe’s diameter before you buy.

During extreme weather conditions, even proper insulation may not be enough to prevent the condensate pipe from freezing. It may help to temporarily run your boiler with the boiler thermostat set as high as possible for as long as the cold spell lasts. But if you continue to experience problems, it’s best to call out a qualified boiler engineer for help.